From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4DCDCC4727E for ; Fri, 25 Sep 2020 08:16:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E64F42085B for ; Fri, 25 Sep 2020 08:16:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="F/txyV+e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727723AbgIYIQH (ORCPT ); Fri, 25 Sep 2020 04:16:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727063AbgIYIQH (ORCPT ); Fri, 25 Sep 2020 04:16:07 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 34AC3C0613CE; Fri, 25 Sep 2020 01:16:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ZgLaEQC68e3osNgfcIO9sC8Nptsdd/ClKs7+Bia7+kw=; b=F/txyV+eBo5XBPj0NJcZTnQdIq GNgRwctMGuVIVJZbmGpZgFenxsBE4CYdCw8MBhiea6kPhSZI7ydVJTY6/ldjFu3nBBEJm955Z7gRS XIoiYCcIQmxcrlJ8FoFffN5rVX0Zxz/oLboLPtUxwRSZ0K7azhuqOsn3VuoTgSSfgdqNIOx7fL15+ 7yBLhuSHc+BvUdtmnsdqnEH4bZWuFlU5+7E7WFDoZFs6fNDBRuYXl8XUsgpY1PqFKfYCsL8+RSvDQ ZCE/n3+2YVeFS5LDyaqZ3ZpMak7NvGBz48LIS+nFrC4W0w8cNMzeAoTZP/5Z5cjXhFRuZhQOo56HB kZevFGIQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kLitV-0006lZ-Ij; Fri, 25 Sep 2020 08:15:53 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 8280B302753; Fri, 25 Sep 2020 10:15:52 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 65EAF20BCC910; Fri, 25 Sep 2020 10:15:52 +0200 (CEST) Date: Fri, 25 Sep 2020 10:15:52 +0200 From: Peter Zijlstra To: Uladzislau Rezki Cc: Mel Gorman , "Paul E. McKenney" , Michal Hocko , LKML , RCU , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Thomas Gleixner , "Theodore Y . Ts'o" , Joel Fernandes , Sebastian Andrzej Siewior , Oleksiy Avramchenko , Mel Gorman Subject: Re: [RFC-PATCH 2/4] mm: Add __rcu_alloc_page_lockless() func. Message-ID: <20200925081552.GS2628@hirez.programming.kicks-ass.net> References: <20200921160318.GO12990@dhcp22.suse.cz> <20200921194819.GA24236@pc636> <20200922075002.GU12990@dhcp22.suse.cz> <20200922131257.GA29241@pc636> <20200923103706.GJ3179@techsingularity.net> <20200923154105.GO29330@paulmck-ThinkPad-P72> <20200923232251.GK3179@techsingularity.net> <20200924081614.GA14819@pc636> <20200924111907.GE2628@hirez.programming.kicks-ass.net> <20200924152112.GB19013@pc636> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200924152112.GB19013@pc636> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 24, 2020 at 05:21:12PM +0200, Uladzislau Rezki wrote: > On Thu, Sep 24, 2020 at 01:19:07PM +0200, Peter Zijlstra wrote: > > On Thu, Sep 24, 2020 at 10:16:14AM +0200, Uladzislau Rezki wrote: > > > The key point is "enough". We need pages to make a) fast progress b) support > > > single argument of kvfree_rcu(one_arg). Not vice versa. That "enough" depends > > > on scheduler latency and vague pre-allocated number of pages, it might > > > be not enough what would require to refill it more and more or we can overshoot > > > that would lead to memory overhead. So we have here timing issues and > > > not accurate model. IMHO. > > > > I'm firmly opposed to the single argument kvfree_rcu() idea, that's > > requiring memory to free memory. > > > Hmm.. The problem is there is a demand in it: People demand ponies all the time, the usual answer is: No.